全文获取类型
收费全文 | 494273篇 |
免费 | 6801篇 |
国内免费 | 2973篇 |
专业分类
电工技术 | 9447篇 |
技术理论 | 5篇 |
综合类 | 1671篇 |
化学工业 | 75196篇 |
金属工艺 | 20194篇 |
机械仪表 | 14776篇 |
建筑科学 | 12095篇 |
矿业工程 | 3007篇 |
能源动力 | 11613篇 |
轻工业 | 43714篇 |
水利工程 | 5433篇 |
石油天然气 | 10658篇 |
武器工业 | 286篇 |
无线电 | 55742篇 |
一般工业技术 | 96498篇 |
冶金工业 | 90897篇 |
原子能技术 | 11639篇 |
自动化技术 | 41176篇 |
出版年
2021年 | 4271篇 |
2019年 | 3837篇 |
2018年 | 6385篇 |
2017年 | 6381篇 |
2016年 | 6909篇 |
2015年 | 4910篇 |
2014年 | 8140篇 |
2013年 | 21618篇 |
2012年 | 13424篇 |
2011年 | 18157篇 |
2010年 | 14376篇 |
2009年 | 15916篇 |
2008年 | 16913篇 |
2007年 | 17118篇 |
2006年 | 14866篇 |
2005年 | 13366篇 |
2004年 | 12637篇 |
2003年 | 12101篇 |
2002年 | 11878篇 |
2001年 | 11972篇 |
2000年 | 11218篇 |
1999年 | 11588篇 |
1998年 | 26742篇 |
1997年 | 19304篇 |
1996年 | 14922篇 |
1995年 | 11410篇 |
1994年 | 10218篇 |
1993年 | 10138篇 |
1992年 | 7634篇 |
1991年 | 7287篇 |
1990年 | 7233篇 |
1989年 | 7199篇 |
1988年 | 6686篇 |
1987年 | 5915篇 |
1986年 | 5929篇 |
1985年 | 6596篇 |
1984年 | 6264篇 |
1983年 | 5793篇 |
1982年 | 5236篇 |
1981年 | 5490篇 |
1980年 | 5211篇 |
1979年 | 5166篇 |
1978年 | 5144篇 |
1977年 | 5515篇 |
1976年 | 7230篇 |
1975年 | 4474篇 |
1974年 | 4267篇 |
1973年 | 4294篇 |
1972年 | 3662篇 |
1971年 | 3265篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
81.
Albrecht Jason E.; O'Brien Edward J.; Mason Robert A.; Myers Jerome L. 《Canadian Metallurgical Quarterly》1995,21(2):364
An implicit assumption of several causal reasoning models is that readers adopt the goals of a narrative's protagonist during text comprehension. In apparent violation of this assumption, readers participating in Experiment 1 of the present study drew inferences relevant to a protagonist's goal even when that goal was already satisfied from the perspective of the protagonist. In Experiments 2 and 3, participants were explicitly asked to view the text situation from the point of view of the protagonist. In this case, the goals of the reader and the protagonist should be the same. In these experiments, participants focused on the goals of the protagonist only when those goals had not been satisfied from the perspective of the protagonist. These results are discussed in terms of reader- and character-based perspectives and in terms of text characteristics that cue perspective taking. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
82.
P Rutgeerts 《Canadian Metallurgical Quarterly》1996,19(1):44-46
Absorbable and nonabsorbable buried sutures were studied in primary cleft lip repair. Group 1 (N = 56) consisted of patients repaired with buried nonabsorbable material (monofilament nylon). Group 2 (N = 47) consisted of patients repaired with absorbable materials (polyglyconate, polydioxanone). All patients were monitored for 12 months. There were stitch abscesses in Group 1 (14%). There were no abscesses in Group 2. This difference was significant (p = 0.007). Abscesses were located in the suture line with no identifiable distribution. There was no significant difference in the cosmetic appearance of the scars in Groups 1 and 2. These results support the view that absorbable sutures are preferable to nonabsorbable sutures for primary cleft lip repair. 相似文献
83.
84.
Auld B.A. Chimenti D.E. Shull P.J. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1996,43(2):319-325
The transverse resonance approach to guided wave analysis is applied to shear horizontal (SH) wave propagation in periodically layered composites. It is found for SH waves that at high values of the guided wavevector β, the wave energy is trapped in the slower of the two media and propagates accordingly at the slower wavespeed. At low values of β, however, the modes demonstrate a clustering behavior, indicative of the underlying Floquet wave structure. The number of modes in a cluster is observed to correlate with the number of unit cells in the layered plate. New physical insights into the behavior of these systems are obtained by analyzing the partial waves of the guided SH modes in terms of Floquet waves. We show that the fast and slow shear waves in the periodically layered composite play an analogous role to the longitudinal and shear partial waves comprising Lamb waves in a homogeneous plate 相似文献
85.
K Alanko L Kanerva B Mohell-Talolahti R Jolanki T Estlander 《Canadian Metallurgical Quarterly》1996,35(4):647-648
The biotransformation of oxazepam by Bifidobacterium bifidum was studied. The major metabolite was purified by chromatographic methods and found to be desmethyldiazepam using NMR, IR and other physicochemical data. 相似文献
86.
87.
T P?usa P Górski H Frank-Piskorska M Kowalski J Kruszewski P Kuna M Kurek R Kurzawa W Silny E Zawisza 《Canadian Metallurgical Quarterly》1996,1(4):292-293
A review of isolates of Neisseria meningitidis and other laboratory evidence of meningococcal infection was carried out for the period 1990-1995. Thirty-three patients with evidence of meningococcal disease were identified over the six year period. Group B organisms were the most commonly identified, but an increase in Group C has occurred and is almost equal in number. Data from clinical, laboratory and public health sources should be centralized in a National Surveillance Centre. 相似文献
88.
Thanapalan Murugesan G. S. Venkat Rathnam S. Panduranga Rao P. Gangadhar Rao 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):290-294
In the present study of gas–liquid contactors, mean residence/contact time was calculated from knowledge of superficial velocity and the gas phase hold-up, for various gas rates and impeller geometry and speeds, and compared with values obtained from RTD measurements. A new correlation, involving Flow Number, Froude Number, system geometry and the physical properties, is proposed. This uses the authors data and those available in literature. 相似文献
89.
90.
Lewis Gloria J.; Greenburg Sharon L.; Hatch David B. 《Canadian Metallurgical Quarterly》1988,19(1):81
We report the results of the first national survey of psychologists in private practice regarding their participation in peer consultation groups. The sample (71% return) was drawn from 800 randomly selected psychologists listed in the National Register of Health Service Providers in Psychology. We found that 23% of the sample currently belonged to peer consultation groups, and 24% had belonged in the past. Of those not currently in groups, 61% expressed the desire to belong if one were available. There were virtually no significant demographic differences between current members and nonmembers. We examined the following group characteristics: formation, length of existence, size, membership, leadership, theoretical orientation, range of experience, time and place, content, and group process. Groups tended to be small, informal, and leaderless; however, we found great variation among groups on all dimensions. Findings also showed a high degree of satisfaction with membership. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献